1. Field of the Invention
The invention relates to a composition, in a particular embodiment to a cosmetic composition, comprising an aminophenol derivative, as well as to the uses thereof. The invention also relates to a process for dissolving an aminophenol derivative.
2. Background
For several years, considerable effort has been devoted to proposing harmless topical depigmenting substances that show good efficacy.
These substances are particularly sought in order to treat regional hyperpigmentations caused by melanocyte hyperactivity, such as idiopathic melasmas, occurring during pregnancy (“pregnancy mask” or chloasma) or during oestro-progestative contraception, localized hyperpigmentations caused by hyperactivity and proliferation of benign melanocytes, such as senile pigmentation marks known as actinic lentigo, accidental hyperpigmentations or depigmentations, possibly due to light-induced sensitization or to post-lesional cicatrization, as well as certain leukodermas, such as vitiligo. For the latter (in which the cicatrizations can result in a scar which gives the skin a whiter appearance and leukodermas), failing the ability to repigment the damaged skin, the regions of residual normal skin are depigmented in order to give the skin an overall uniform white complexion.
Various depigmenting agents have been proposed in the prior art. In particular, it has been demonstrated that certain aminophenol derivatives have the ability to inhibit melanogenesis, even at low concentrations, without showing any cytotoxicity. These compounds, as well as the method for preparing them, are disclosed in patent application WO 99/10318 and are aminophenols containing a relatively long or short hydrocarbon-based chain, preferably an alkoxycarbonyl chain, linked to the nitrogen atom. They have the drawback of being only sparingly or not at all soluble in water. For the short-chain hydrocarbon-based compounds, their introduction into cosmetic compositions requires a dissolution in aqueous-alcoholic solution, which is not always desirable when the composition is intended, for example, to be applied to the area around the eyes. In addition, it has been noted that aqueous-alcoholic gels have a tendency to trap these compounds in their network, thus limiting their diffusion into the malpighian epidermis.
As regards the long-chain hydrocarbon-based compounds, they are insoluble in oils, on account of their stearic bulk, and have a tendency to recrystallize in water. In patent application FR-99/09663, it has been proposed to incorporate them into the bilayer of lipid vesicles in order to facilitate their formulation in cosmetic products. However, this inclusion involves an implementation which is occasionally intricate.
It thus remains necessary to be able to dissolve these aminophenol derivatives readily in a physiologically acceptable medium which entails a minimum of discomfort when applied to the skin or the scalp, and which is easy to use. In addition, it is necessary to be able to dissolve an amount of these compounds which is sufficient for cosmetic or dermatological use, without recrystallization of these compounds or loss of stability of the composition containing them. The reason for this is that this instability would result in a greater or smaller loss of efficacy of these compositions and/or in a change in their appearance, which would run the risk of putting users off using them.